Inspection device for objects with a spherical surface

ABSTRACT

A device ( 1 ) for inspecting objects with a substantially spherical surface, such as for example eggs or fruit, comprises optical observation means ( 8 ) for observing the objects. The device has a supporting surface ( 10 ) for supporting the objects. There is a light source for illuminating the objects. The device also comprises a box ( 2 ) with reflective walls ( 3   a   , 4   b  and  4   a  shown) which is positioned above the supporting surface ( 11 ). The light source and the observation means ( 8 ) are accommodated in the box ( 2 ). A plurality of objects can be placed next to one another on the supporting surface ( 10 ) and can be illuminated equally well.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/NL2004/000655, filed Sep. 21, 2004, which claims the benefit ofNetherlands Application No. NL 1024619, filed Oct. 24, 2003, thecontents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a device for inspecting objects with asubstantially spherical surface, such as for example eggs or fruit,comprising optical observation means for observing the objects, asupporting surface for supporting the objects and a light source forilluminating the objects.

BACKGROUND OF THE INVENTION

When inspecting objects by means of optical observation means, theillumination of the objects is very important for the results of theinspection. In general, it is desirable for shadowing caused bynon-uniform illumination, for example during the inspection of thesurface of round objects, to be avoided. Shadows may be incorrectlyregarded by the optical observation means as dirt or irregularities,which is deleterious to the inspection.

A device of this type is known. WO 03/023455 has disclosed a device inwhich light sources are positioned obliquely above and next to aconveyor in order to provide uniform illumination of the objects overthe entire region in which the observation means observe the objects.The known device may have a plurality of conveyors arranged next to oneanother, in which case light sources are arranged next to and obliquelyabove each conveyor. In this case, light sources of a conveyor alsoilluminate the adjacent conveyor. In the known device, the light sourceshave to be positioned accurately in order to obtain uniform illuminationof the objects. Furthermore, sufficient light sources per conveyor haveto be provided. Furthermore, this arrangement of the light sources nextto the conveyor means that only one or two objects can be placed next toone another on a conveyor to achieve good illumination.

Another device of the type referred to in the preamble is known from FR2 699 696. This known device can be used, for example, to inspect theripeness of fruit. The device comprises a box which is positioned abovea reference plane. The reference plane may be moveable, so that objectsare transported through the box. A ring of a transparent material isarranged approximately halfway up the height of the box. A light sourcewhich radiates light into the ring through an opening in the box isarranged outside the box. The ring transmits the light and isresponsible for uniform illumination of the object, which is locatedbeneath it approximately in the centre. An optical observation means isarranged in the top of the box for observing objects. The opticalobservation means as it were look at the object through the centralopening in the ring. This known device is designed to illuminate andobserve one object each time and is therefore not suitable for theinspection of large numbers of objects.

SUMMARY OF THE INVENTION

This object is achieved by a device of the type mentioned in thepreamble which is characterized in that the device comprises a box withreflective walls which is positioned above the supporting surface and inwhich the light source and the observation means are accommodated.

The design according to the invention causes light which is emitted bythe light source to be reflected by the reflective walls and then lightwhich is reflected by the walls to be reflected again by the otherwalls. This results in a constantly recurring light source which createsuniform illumination of the objects without the need for complicatedpositioning of the light sources. In theory, a uniform light sourcewhich recurs infinitely on all sides would be produced if walls with acoefficient of reflection of 1 are used.

In a preferred embodiment of the invention, the supporting surfacecomprises a conveyor for conveying the objects through the box past theobservation means, with the result that large numbers of objects perunit time can be observed by the observation means and a highlyexpedient arrangement is achieved.

The invention will be explained in more detail with reference to thedrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view, obliquely from above, of a preferredembodiment of a device according to the invention.

FIG. 2 shows a perspective view, obliquely from below, of a portion ofthe device shown in FIG. 1.

FIG. 3 shows a cross section through a portion of the top side of thedevice shown in FIG. 1.

FIG. 4 shows a cross section through the box of the device shown in FIG.1, on line IV-IV in FIG. 5.

FIG. 5 shows a side view of the box of the device shown in FIG. 1.

FIG. 6 shows a front side view of the box of the device shown in FIG. 1.

FIG. 7 shows a front view of a conveyor for eggs.

FIG. 8 shows a plan view of the conveyor shown in FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a perspective view of advice 1 according to the invention.The device 1 comprises a box 2 with four side walls 3 a, 3 b, 4 a, 4 b.For the sake of clarity, the view shown in FIG. 1 is cut away by virtueof the front side wall 3 b being omitted from the figure. Furthermore,the box 2 has a top wall, which is likewise omitted from FIG. 1 for thesake of clarity. In the embodiment shown, the width of the side walls 3a and 3 b is greater than that of the side walls 4 a and 4 b.

FIG. 2 shows a perspective view, obliquely from below, of the box 2illustrating the side walls 3 b and 4 a. Furthermore, the top side 5 ofthe box is visible. Strip Lights 6 are arranged at regular intervals onthe top side 5 of the box 2. In FIG. 2, the strip lights 6 are notcovered. However, it is preferable for them to be covered by one or morediffuser plates 7 made from a matt transparent material, for examplemilky-white glass or plastic, as shown in FIG. 3. The strip lights 6together form a light source which is not completely uniform but is mademore uniform by the diffuser plate 7. These diffuser plates 7 form thetop wall of the box 2. This arrangement of the strip lights 6 and thediffuser plate 7 means that the box 1, on the top side 5, has a lightsource with a substantially even light plane directed towards the insideof the box 2. This even light plane emits light downwards in alldirections in a uniform way.

FIGS. 4-6 show a preferred embodiment of the box 2. This box 2 comprisesa frame which is composed of four upright section pieces 19 and top andbottom longitudinal section pieces 20 a, 20 b, as well as top and bottomtransverse section pieces 21 a and 21 b, the longitudinal and transversesection pieces 20 a, 20 b, 21 a, 21 b being positioned perpendicular tothe upright section pieces 19 and connecting the latter to one another.The upright section pieces 19 are designed to be supported by a floorsurface. The side walls 3 a, 3 b, 4 a and 4 b of the box 2 are securedto the frame, as shown in FIGS. 5 and 6. In the preferred embodimentshown, the side faces 4 a and 4 b are formed from two parts, asillustrated in FIG. 6. These two parts are formed as access doors 40which are hinged or slideably secured to the frame. Access to the insideof the box 2 can be gained via the access doors 40. The side faces areproduced from metal sheet and have a mirroring surface, preferably witha high coefficient of reflection, facing towards the inside of the box2. It is preferable for the coefficient of reflection to be 0.8 orhigher. The side faces of the box 2 according to the invention thusfunction as mirrors. This is different than known inspection devices, inwhich the inner side of the box reflects the light diffusively, e.g. byapplying white matt paint to the inner side.

A top cover plate 50 is fitted to the top side of the frame, as can beseen from FIG. 4. The strip lights 6 are arranged beneath this top coverplate 50 (cf. FIG. 2). It is preferable for the cover plate 50 to bemade from reflective material, in order for light which is radiatedupwards from the strip lights 6 to be reflected downwards towards thediffuser plate 7. This results in an even more even light plane at thetop side 5 of the box 2.

Light which is emitted by the strip lights 6 via the diffusor plate 7into the box is reflected by the reflective walls 3 a, 3 b, 4 a and 4 b.Also, light reflected by the respective side walls 3 a, 3 b, 4 a, 4 b isreflected again by the other side walls 3 a, 3 b, 4 a, 4 b. As a resultof the mirroring side walls a light source recurring as a mirror imageon all sides is produced. The higher the coefficient of reflection ofthe walls, the more frequently the light source will recur on all sides.In theory, in the case of walls with a coefficient of reflection of 1, aconstantly recurring light source would be produced. The illuminationfrom all sides means that the illumination of a separate object 12 is nolonger dependent on the position of the said object 12 on the conveyor10 and therefore means that a plurality of objects can be placed next toone another on a conveyor and can be illuminated equally well.

One or more conveyors 10 pass through the bottom of the box 2. In thesituation shown in FIG. 1, the box 2 is located above two conveyors 10which are arranged parallel and next to one another and extend parallelto the side walls 4 a and 4 b. Of course, the box 2 may also be usedwith more or fewer conveyors 10 or, for example, with a stationarysupporting surface. Therefore, the conveying direction of the conveyors10 extends substantially parallel to the longitudinal direction of thebox 2, i.e. the width of the side faces 4 a and 4 b. The combined widthof the adjacent conveyors 10 is preferably less than the width of thebox 2, i.e. the width of the side faces 3 a and 3 b, with the resultthat there is a space 30 next to the conveyors 10 in the box 2, in whicha person can stand in order, for example, to eliminate any faults.Objects 12 which are to be inspected, for example eggs or fruit, can beconveyed through the box 2 in rows on the conveyors 10, in the directionillustrated by the arrows 11.

The light source which recurs via the reflective walls 3 a, 3 b, 4 a, 4b provides uniform illumination of the substantially spherical objects12 from all sides, irrespective of whether the object 12 is positionedin the centre or in the vicinity of the edge of the conveyor. This isexpedient for inspection of the objects 12 by means of a camera andoptical data processing, as explained below.

Furthermore, a camera 8 is arranged above the conveyors 10 at the topside 5 of the box 2 in the vicinity of each of the side walls 4 a and 4b. The cameras 8 each have an observation field which extends over theentire width of the conveyors 10 arranged next to one another. Theobservation field preferably extends at least over a centre section ofthe length of the box 2, since in the centre section the illuminationstrength is most even from all sides. Therefore, the objects 12 passedthrough the observation field of the cameras 8 by the conveyor 10 can beobserved obliquely from above from two sides by means of the cameras 8,resulting in a good view of the objects.

It is preferable for there to be openings in the diffuser plate 7 or forthere to be two diffuser plates 7, with a gap between them, throughwhich the cameras, as it were, can look at the conveyor. It ispreferable for the lens of the cameras 8 to be positioned in the planeof the diffuser plate 7. This prevents the diffuser plate 7 fromrestricting the observation area of the cameras 8. However, should thecameras 8 project beneath the diffuser plate 7, they would allow ashadow to form in the box 2.

It is preferable for the conveyor 10 to be designed in such a mannerthat the objects 12 execute a rolling movement as they are beingconveyed. This type of conveyor is known from the prior art, and FIGS. 7and 8 show an example of a conveyor of this type for eggs. The rollingmotion of the objects 12 allows each camera 8 to observe each object 12over its entire circumference.

The cameras 8 are preferably in each case coupled to a computer 13 via adata link 14. The images recorded by each camera 8 can be fed to thecomputer 13, where they can be combined in a manner which is known perse with the aid of image-processing software and are compared withpredetermined reference values. If an object 12 has, for example, asoiled surface, this can be determined in the computer 13 as a result ofthe colour or pattern of spots of the object 12 deviating excessivelyfrom the reference. The computer 13 can record the position of thedeviating object 12 on the conveyor 10 and emit a control signal to aremoval device (not shown) located further downstream in order forobjects which deviate excessively to be automatically removed from theconveyor 10. It should be noted that this automatic selection andremoval may also be effected in other ways and is no way essential tothe invention.

1. Inspection device for inspecting eggs or fruit with a substantiallyspherical surface, comprising: a conveyor adapted to convey a pluralityof eggs or fruit placed next to each other in a direction transverse tothe conveying direction, at least one camera for observing the eggs orfruit on the conveyor, a box having a mirroring surface which ispositioned above the conveyor and in which the at least one camera isaccommodated, the mirroring surface consisting essentially of fourreflective side wall mirrors having a coefficient of reflection of atleast 0.8, where the four reflective side wall mirrors are side wallsthat define the box, and a light source which is accommodated in the boxopposite the conveyor for illuminating the eggs or fruit from above, thelight source having a substantially even light plane directed towardsthe inside of the box, and which light source, as a result of themirroring side walls, recurs on all sides so as to provide uniformillumination of the eggs or fruit on the conveyor from all sides. 2.Inspection device according to claim 1, wherein the box is substantiallyrectangular and has a top cover plate joining the four reflective sidewalls.
 3. Inspection device according to claim 1, wherein the reflectiveside walls are made from metal.
 4. Inspection device according to claim1, wherein the light source is arranged on the top side of the box. 5.Inspection device according to claim 4, wherein the light source has auniform radiation plane.
 6. Inspection device according to claim 4,wherein the light source comprises one or more lamps which aredistributed substantially uniformly.
 7. Inspection device according toclaim 5, wherein the light source is arranged beneath the top coverplate above one or more diffusor plates.
 8. Inspection device accordingto claim 1, wherein the device has at least two cameras which arearranged on opposite sides of the box.
 9. Inspection device according toclaim 1 wherein the device comprises a computer which is coupled to theat least one camera in order to compare the observations withpredetermined reference values for automatic selection of the eggs orfruit.
 10. Inspection device according to claim 1, wherein the conveyoris designed in such a manner that the eggs or fruit execute a rollingmovement as they are being conveyed.